If you thought the regular seasonal flu has been late making its annual appearance, you might be surprised to learn that based on recent history, it's right on time.

February is again proving to be the peak time for cases of influenza in Illinois and across the nation. According to the Illinois Department of Public Health, the number of people with the flu is spiking, and many more people are likely to fall ill before the season ends.

"For the last 30 years in the United States, February has been the prime month for illness with the regular seasonal flu, though infections can occur in April and as late as May," Dr. Michael Koller, an internal medicine physician at Loyola University Health System. tells me.

The H1N1 strain, also known as "swine flu," is still around, but it's not as widespread. This year's flu vaccine contains the H1N1 strain as well as two others – the Perth H3N2 virus and the B Brisbane virus. Fortunately, this year's vaccine has been a good match to the strains circulating in the United States. So getting a vaccine this late in the season can still offer protection, even if flu activity has already started.

Doctors used to advise getting a flu shot only in October and November. Now doctors vaccinate through February because it only takes about two weeks to develop an antibody response after the flu shot.

The flu, or influenza, is a highly contagious viral infection that attacks the respiratory system.

Each year in the U.S. between 5 to 20 percent of the population contracts the flu. The Centers for Disease Control and Prevention (CDC) has a universal recommendation this year that children age 6 months and older get an influenza vaccination.

The CDC also recommends vaccinations for people ages 50 and older and for anyone with a chronic illness such as asthma, diabetes or heart disease. This includes people who have weakened immune systems and those infected with HIV, the virus that causes AIDS.

In our area, flu appears almost only during the winter. If you are experiencing flulike symptoms, it is best to act fast and speak to your doctor within 12 to 48 hours.

Since 2009, Loyola has required mandatory flu shot for all employees, faculty, medical and nursing students and other allied groups who work or have clinical training at Loyola's campus in Maywood and its suburban health centers. For the second consecutive year, more than 99 percent of those covered by the policy received vaccinations. Also, all visitors with coughs to my office in Oak Park, as in any Loyola facility, are being asked to wear masks as are hospital employees who were medically exempt from Loyola's mandatory flu shot policy.

"Mandating flu shots for all our employees is absolutely the right thing to do," said Dr. Jorge Parada, director of infection prevention and control at LUHS. "The simple fact is that this is the profession that we have all chosen. The last thing we should be doing is putting our patients at risk when it is totally unnecessary. This is big safety issue."

As well as the spike in flu cases, Loyola and other hospitals are seeing an increase in the number of patients with respiratory syncytial virus (RSV), an infection of the small airways of the lungs that is also known as bronchiolitis.

"RSV is one of those respiratory viruses that can produce flulike symptoms," Parada said. "In adults, it's generally mild. In young children, especially babies and children with respiratory problems, it can be life threatening and those children require immediate medical attention."

Like the flu, RSV is highly contagious. It can be spread by physical contact with someone who is infected and through the air by coughing and sneezing. Basic hygiene like washing your hands and covering your mouth when coughing and sneezing can help prevent the spread of both illnesses.